Selective hydrodesulfurization process



March 4, 1952 U FRANKUN 2,587,987

SELECTIVE HYDRODESULFURIZATION PROCESS Filed May 10, 1949 GASOLINE 115 PRIMARY DISTILLATiON UNIT NAPHTHA 92 PREHEATED CRUDE OIL CHARGE 1o LT. GAS OIL ,65

HY. GAS OIL BOTTO M5 74 9a 124 a a i 1 50 -76 "100 I 80 i 104: i 1 i 1 -a -J J1 126 HYDROGEN CHARGE 76 102 126 SELECTIVE HYDRO DESULFURIZATION FD ED BED RELflCTORBB Iii 13 136 INVENTOR.

1&0 LE LIE- FR NKLIN BY fi' W- w i 152 PRODUCT TO k FRACTIONATION STILL v I 144 150 Y W ETTORNEY Patented Mar. 4, 1952 SELECTIVE HYDRODESULFURIZATION PROCESS 1 Leslie U. Franklin, Port Arthur, Tex., assignor to Gulf Oil Corporation, Pittsburgh, Pa., a cor-- poration of Pennsylvania Application May 10, 1949, Serial No. 92,385

12 Claims.

This invention relates to a selective hydrodesulfurization process and more particularly to an improved method of conducting hydrodesulfurization reactions.

The various hydrodesulfurization processes have proved to be of great importance for the desulfurizing of sulfur-containing petroleum hydrocarbons. The methods of conducting this process are broadly divisible into two basic types, namely the catalytic hydrodesulfurization methd and the contact hydrodesulfurization process. The former encompasses those methods in which the sulfur contained in the charge stock is removed therefrom in the form of a gas such as hydrogen sulfide, by the catalytic action of a catalytic material having hydrogenating characteristics such as nickel, nickel oxide, the iron group metal molybdates, sulfides, molybdenum compounds, etc. The contact" method on the other hand removes the sulfur by chemically combining it with a contact agent which should be one possessing hydrogenating characteristics such as an iron group metal, metal oxide or combination thereof deposited on a carrier. The sulfur is removed from the charge stock by being absorbed as metallic sulfide on the contact agent and the process is discontinued when the iron group metal content of the contact has been substantially converted into iron group metal sulfide, and the contact is regenerated.

Among the major difiiculties encountered with both processes is the undue amount of hydrogen consumption causing concomitant abnormally large facilities for the preparation and storage of hydrogen. An equally great or greater impediment in these processes is the diminution of cata lyst activity, and the shortening of catalyst life due to the deposition of coke and carbon upon the catalyst. Notonly does this deposition cause the catalytic activity to diminish and consequently decrease the useful on-stream period, but also the coke causes a pulverization and powdering of the contact bed, hence reducing the over-all catalyst life. In turn the adverse effect on the catalyst causes an increased amount of cracking of the charge stock. The problem of hydrogen consumption is also intimately correlated with the coke deposition in that large amounts of hydrogen are wasted by reacting with the coke, or with the cracked charge stock due to the catalytic activity of the coke, to form low boiling gaseous hydrocarbons, such as methane.

Furthermore,

due to the decrease in catalyst activity, larger reactor sizes must be utilized to achieve commercial practicality.

This invention has as an object the provision of a hydrodesulfurization process in which the hydrogen consumption is materially reduced;

A further object of this invention is to provide a hydrodesulfurization process in which the activity and life of the catalyst is greatly extended.

A still further object of this invention is to provide a hydrodesulfurization process in which the coke deposition on the surface of the catalyst is materially reduced.

Another object of the present invention is to provide a hydrodesulfurization process in which the size of the reactor is reduced, without reducing the yield of product. Other objects will appear hereafter.

These and other objects are achieved by the present invention which comprises removing sulfur from petroleum hydrocarbons by fractionating a petroleum hydrocarbon charge stock into a plurality of fractions, contacting a high boiling fraction with a contact material having hydrogenating characteristics in the presence of a hydrogen-containing gas, combining a lower boiling fraction with the mixture of said high boiling fraction and hydrogen-containing gas, and contacting the combined mixture with a contact material having hydrogenating characteristics at an incrementally higher temperature.

This invention can be applied with exceptional success to high boiling petroleum hydrocarbon oils, such as total crude containing sulfur. By total crude is meant naturally occurring petroleum oil which has not been processed in any manner, but has been or preferably should be separated from water or sediment and desalted. This same principle can be applied with similarly improved results to any fraction or fractions, obtained from a crude oil, by first subdividing such primary fractions into any desired number of subsidiary fractions and hydrodesulfurizing them in the inverses order of their boiling ranges at incrementally higher temperatures, in the manner described herein for the primary fractions.

I have found that the optimum hydrodesulfurization conditions vary with the boiling point range of a petroleum hydrocarbon fraction. Hence by fractionating a crude charge stock prior to hydrodesulfurizing and recombining these fractions as described, definitive optimum conditions of time, temperature, and hydrogen to oil ratio will be obtained for each fraction. By hydrodesulfurizing crudes in this manner, namely by recombining so as to subject each fraction to its optimum time, temperature and hydrogen to oil ratio conditions, highly superior hydrodesulfurization results may be achieved. Furthermore, I have found that by treating the various charge stock fractions in inverse hydrodesulfurization temperature relationship to the boiling point range of the petroleum fraction the superior results of the present invention may be achieved.

Besides increasing the temperature with the addition of each lower boiling fraction, I have found that the higher boiling fractions, such as reduced crude oil, which are more resistant to hydrodesulfurization, tend to thermally crack and deposit coke on the catalyst more readily than do the more thermally stable lower boiling fractions such as gasoline which are less resistant to hydrodesulfurization, and that this deposited coke which stems mainly from the higher boiling fractions decreases the catalyst activity, increases thermal cracking, increases hydrogen consumption,:and increases the catalyst regeneration requirements. The coke deposition is accelerated by increasing the temperature and contact time. The rate of this acceleration is much greater with the higher'boiling fractions than with the lower boiling fractions. I have found that the rate of coke deposition from the higher boiling fractions is substantially reduced by partially hydrogenating them at lower temperatures, such as between 700 F. and 750" F. at relatively long contact times, and then gradually increasing the temperature while simultaneously decreasing the contact time. By this method of processing, the higher boiling fractions are incrementally fortified with hydrogen'to make them more resistant to thermal decomposition at the incrementally higher temperatures which are required for increased degrees of hydrodesulfurization. The lower boiling fractions, which are normally richer in hydrogen when obtained from the crude oil, require less prehydrogenation before being subjected to the higher temperatures 'for hydrodesulfurization. They also require shorter contact times at these higher temperatures.

While the application of my process to hydrodesulfurization reactions will result in improved process circumstances, my process is afiected by suchv variables as type of catalyst, hydrogen-oil.

ratio, over-all space velocity, system pressure, etc., in a manner similar to their effects on conventional processes. a

For the purposes of illustration I shall indicate the application of the present invention to a contact hydrodesulfurization process. However, as will be indicated hereafter, the invention is equally applicable to catalytic hydrodesulfurization methods. To more fully understand the nature of my invention, reference should be made to the accompanying diagram in which preheated crude oil charge enters primary distillation unit 12 by means of line H]. In primary distillation unit l2 the crude charge is fractionated into a plurality of fractions. In the accompanying figure, I have indicated the fractionation as producing 5 fractions, namely, gasoline, naphtha, light gas oil, heavy gas oil and crude oil bottoms. By gasoline,

is meant those hydrocarbons in the crude charge stock boiling in the range of between 100 to 400 F. The naphtha fraction connotes the fraction distilling after the gasoline fraction, namely, the material having a boiling range of about 350? F to...

525 F. The light gas oil fraction is that fraction which distills after the naphtha fraction and boils over a range of about 500 to 600 F. The heavy gas oil comprises the fraction boiling between about 600 to 650 F. The bottoms is the material left after the previously mentioned fractions have been distilled from the crude. The crude oil charge may be fractionated into a larger or smaller number of fractions, but I have found that optimum results are obtained when the fractions approximate those given in the accompanying flow diagram.

The bottoms from primary distillation unit l2 are removed by means of line I4 and pass through cooler l6, line l8 into accumulator 20. The amount of bottoms in accumulator 20 is controlled by level controller 22 which is in series with pump 24. From accumulator 20 the crude oil bottoms pass through line 26, pump 24 into line 28. In line 28 the bottoms are joined by hydrogen-containing gases which enter the system by means of line 30. This mixture of hydrogen-containing gases and crude oil bottoms passes through line 32 into heater 34. In heater 34 the crude oil bottoms are heated to the desired reaction temperature for the initial portion of the hydrodesulfure ization process, and this mixture is passed by means of line 36 into the uppermost portionof reactor 38 which comprises zone I. The tem-, perature of the hydrogen-containin gas and crude oil bottoms mixture in zone I is regulated by temperature controller 40 attached to heater. 34 and zone I.

In zone l the mixture of bottoms and hydrogencontaining gas passes over beds of contact material having hydrogenating characteristics. This contact material is preferably a member of the iron group metals, i. e., nickel, iron or cobalt and may be in the free metallic state or in the form of metal oxide or as a combination of free metal and oxide. In all cases the contact material should be supported on a carrier. I have found that of the iron group metals, those containing nickel comprise the most advantageous contacts, and that contacts having substantial amounts of nickel oxide constitute the preferred contacts for the purposes of my invention. By carrier, I mean any substances widely used in the petroleum industry for this purpose, such as alumina, kiesel'guhr, silica gel, aluminum silicate, silica-alumina, Alfrax, Magnesol, Porocel, bauxite, diatomaceous earth, etc. The contacts of this invention may be prepared by any of the known methods such as single or multiple impregnation, coprecipitation, adsorption from colloidal solution, etc.

In zone I the bottoms are hydrodesulfurized with at least a significant portion of the sulfur content of the bottoms combining with the irongroup metal content of the contact to form iron group metal sulfide, thereby removing the sulfur from the charge stock. Simultaneously with the removal of sulfur the contact induces a mild hy-;

drogenation of portions of the petroleum hydrocarbons in the bottoms. I have found that the best temperature for zone I is of theorder of 700 F., since at this low temperature mild hydrodesulfurization of the bottoms is effectuatedwith but a minimum amount of cracking and coke deposition.

In primary distillation unit l2 the next lower boiling fraction, namely, the heavy gas oil fraction, is removed by means of line 42 and passes through cooler 44, line 46, into accumulator 48. The level in accumulator 48 is controlled bylevel controller 50 which is attached to accumulator 48,.

and to pump 52. From accumulator 48 the heavy gas oil fraction passes through line 54, pump 52 and into line 58. In line 56 the heavy gas oil fraction is joined by the mixture of crude oil bottoms and unreacted hydrogen which leaves zone I of reactor 38 by means of line 58. This mixture passes through line 60 and enters heater 82 where it is vaporized and heated to a, suitable reaction temperature prior to re-entering reactor 38. From heater 62 the combined mixture passes through line 64 into zone 2 of reactor 38. The temperature of the mixture in zone 2 is regulated by temperature controller 65 which is connected between zone 2 and heater 82. In zone 2 the mixture is hydrodesulfurized by passing over a similar contact to that found in zone I. I have found that a suitabletemperature for zone 2 is of the order of 750 F. and that at this temperature a minimum of cracking and coke deposition is achieved.

The next lower-boiling petroleum fraction, namely, the light gas oil, is removed from primary distillation unit I2 by means of line 68 and passes through cooler I0, line I2 into accumulator I4. The level in accumulator I4 is controlled by level controller I8 attached to pump I8. The light gas oil fraction passes from accumulator I4 through line 80, pump I8 into line 82. In line 82 the light gas oil fraction is joined by the hydrodesulfurized mixture of bottoms and heavy gas oil fractions and unreacted hydrogen-containing gas which leaves zone 2 by means of line 84. This combined mixture then passes through line 88 into heater 88 where the unvaporized constituents are vaporized and the Whole mixture is heated to a reaction temperature suitable for zone 3 of reactor 38. From heater 88 the mixture passes by means of line 90 into zone 3. The temperature of the mixture in zone 3 is regulated by temperature controller 8'! which is connected between heater 88 and zone 3. In zone 3 this combined mixture is hydrodesulfurized by passing over a contact material similar to that found in zones I and 2. I have found a temperature of the order of 800 F. to be suitable for this zone.

The naphtha fraction leaves primary distillation unit I2 by means of line 92, and passes through cooler 94, line 98 into accumulator 98. The level in accumulator 98 is controlled by level controller I00 which is attached to pump I02 and accumulator 98. The naphtha fraction leaves accumulator 98 through line I04 and passes through pump I02 into line I06. In line I08 the naphtha fraction is joined by the hydrodesulfurized mixture and unreacted hydrogen-containing gas which has left zone 3 through line I08. This newly combined mixture then passes through line H0 into heater H2. In heater H2 vaporization of the unvaporized portions are effected and the mixtures are heated to a suitable temperature for the hydrodesulfurization conditions maintained within zone 4. The combined mixture is then passed from heater H2 through line H4 and enters zone 4 of reactor 38. In zone 4 the combined mixture is hydrodesulfurized by passing over a similar contact to that found in zones I, 2 and 3. I have found that a suitable temperature for zone 4 should be of the order of 850 F. The temperature conditions of zone 4 are regulated by means of temperature controller H6 which joins zone 4 to heater H2.

The lowest boiling fraction, 1. e., the gasoline,

leaves primary distillation unit I2 through line H8 and passes through cooler I20, line I22 into accumulator I24. The level in accumulator I24 accumulator I24 and pump I28. The gasoline fraction passes from accumulator I24 through line I30, pump I28 into line I32. In line I'32 the gasoline fraction is joined by the hydrodesulfurization products and unreacted hydrogen-containing gas mixture from zone 4 which enters line I32 .by means of line I34. This final combined mixture passes from line I32 through line I36 into heater I38. In heater I38 this mixture is vaporized and heated to a temperature appropriate for hydrodesulfurization in zone 5 of reactor 38. From heater I38 the mixture passes through line I40 into zone 5 of reactor 38. In zone 5 the mixture is hydrodesulfurized over a similar contact material to that found in zones I to 4. I have found that a temperature of about 900 F. is a suitable temperature for this zone. The temperature in zone 5 is controlled by temperature controller I42 which joins zone 5 and heater I38.

From zone 5 the fully hydrodesulfurized crude and the unreacted hydrogen-containing gas is passed by means of line I44 through back pressure controller valve I50. From back pressure controller valve I50 the product is passed to a fractionation still by means of line I52 and thence refined and freed from gaseous contaminants in the customary manner.

The process is continued until regeneration of the contact is required. This is usually commenced when substantial amounts of hydrogen sulfide appear in the eflluent. An empirical method for determining when the regeneration .is to be commenced is to begin regeneration when the contact contains from 30 to 60% iron group metal sulfide. In some instances when the commercial situation permits the removal of minor amounts of hydrogen sulfide from the product the process may be continued until the entire metal content of the contact has become converted into metallic sulfide. The regeneration of the contact to its original form may be effected by any of the customary prior art methods, such as oxidation etc.

The following "example is illustrative of the improvements which can be realized by the process of my invention:

Two hydrodesulfurization runs were made, the first utilizing the conventional hydrodesulfurization process in which the oil is charged to the reaction zone without prior fractionation; and the second utilizing the selective hydrodesulfurization method of the present invention. Identi cal nickel hydrogenation catalyst was utilized in each run. The results obtained with each hydrodesulfurization process were as follows:

1 Hydrogenation. 8 At top of reactor. 3 Total crude at top of reactor.

4 Five Equal Size Fractions in Five Equal Size Zones Starting with Heaviest Fraction at Top of Reactor.

and to force the oil-hydrogen vapor through the Reaction zoneNo 1 1 Y 2 3 4 5 Total Variable Factors Affecting- Residence Time of Oil Fractions: I

Oil Feed: BbL/Hr. (Liq. Basis). I00. 40 60 80 100 Hydrogen Feed: Cu. FtJBbl.

(approx) (Measured at 60 F. & l Atmos. Press.) 4, 250' 21,250 '10,625 7,080 5,130 4, 250 Temperature: F. 900 700 750 800 85 900 Residence Time in Seconds (Approx): Residence Time in each. Reaction Zon Gasoline Fractiom-" 38. 65 0. O 0. Q 0. 0 0. 0 7. 18 7. 18' .Naphtha Erection- 38.65 0.0 0.0 0.0 8. 36 7.18 15.54 LthGas Oil Fractio 38.65 0.0 0.0 8.82 8.36 7.18 24.36 Hy. Gas 011 Fraction 7 38.65 0.0 9.49 8.82 8.36 7.18 33.85 ReducedCrude 38J65i mos 9.49 8.82 8.36 7.18 43.90 Relative Catalyst Regeneration Rc-- quirement 1.00 0.75

1 Disregarding amount of Hz consumed in preceding zones.

In the above example the length of the process heaters. Alternatively, a free fiowing type of periods before regeneration was 4 hours in both catalyst could be utilized and with a suitably de-' hydrodesuifurization processes. It is to be noted signed heater the catalyst could he allowed to that the relative catalyst regeneration require- 20 flow through the heater with the hydrogen-oil ment for my process was but 0.75 of that required vapors. for the conventional hydrodesulfurization process, This invention permits smaller amounts of due to the fact that there was much less coke hydrogen to be utilized in the course of a hydroto be burned off the catalyst Alternatively, I desulfurization process since there isasignificant could have increased the process period length of decrease in the large amounts of hydrogen normy process to a degree, so as to result in the mally consumed by the formation of low boiling same regeneration requirement as that shown for gaseous hydrocarbon contaminants. This is due the conventional method, and thereby have to the fact that crackin of the crude charge achieved a longer effective on-stream cycle for a stock to low boiling fractions is materially re-' given amount of catalyst. Inaddition, this would duced. Furthermore, the on-stream period of have effected a further decrease in the amount the hydrodesulfurization cycle will be lengthened, of hydrogen consumed per barrel of oil by my since, by the use of this invention, smaller process. This is due to the fact that some hyamounts of coke and carbon will be deposited drogen is consumed by reduction of the catalyst on the catalyst and hence it will not be necessary after each oxidative regeneration cycle. to regenerate the catalyst as frequently as in When the catalytic hydrodesulfurization procthe prior methods. There will be a concomitant ess is utilized, the conditions will be relatively saving of hydrogen since the hydrogen consumpanalogous to those utilized in the contact hytion normally attendant with the reduction of drodesulfurization method. However, since the the catalyst which accompanies the regeneracatalyst may be varied over a much wider range 49 tion is lessened. Also the invention enables the of substances, the specific operational requireuse of the highest hydrogen to oil ratios whenthe ments for this type of process may differ someheaviest portions are most susceptible to carbon what from those given above. As indicative of deposition thus further reducing the formation the wide range of catalysts that may be employed of carbon and gases. in the catalytic hydrodesulfur ization method, I 4 In addition to the foregoing, the contact lifev have found that any of the iron group metals, will be increased since the lessening of the carmetal oxides, mixtures ofmetal and metal oxide, bon deposition reduces the amount of contact or the iron group metal molybdates, may be utidecrepitation and pulverization normally enlized as can molybdenum sulfide, the iron group countered in this process. Furthermore, due to metal sulfides, etc. In all cases, for optimum re- 50 the lengthening of the period of catalyst activity sults the catalyst should be impregnated on a carand hence of the on-stream cycle, the size of the rier. reactor may be decreased, which permits a sub- The aforementioned description should be taken stantial saving in the cost of commercial installaas merely illustrative of the type process that tion. is contemplated by the present invention. In 'WhatI claim is: place of the foregoing five fractions 2. larger or 1. A selective hydrodesulfurization process smaller number of fractions may be utilized. which comprises removing sulfur from petroleum Furthermore, additional hydrogen-containing gas hydrocarbons by fractionatin a petroleum hymay be injected at each stage concurrently with drocarbon charge stock into a plurality of fraceach lower boiling fraction. In addition, in place 6 tions; contacting a high boiling fraction with a of the fixed bed catalyst system herein described, hydrogenation catalyst in the presence of a a downward moving bed of catalyst in which the hydrogen-containing gas, combining a lower regeneration steps are conducted outside of the boiling fraction with the mixture of said high reactor may be utilized, and the process variables boiling fraction and hydrogen-containing gas, would remain similar to those described herein heating thiSmiXtm-e to an incrementally h e for the Stationary The mechanics of temperature and contacting this heated mixture ing the catalyst from one zone to the next may t a hydrogenation catalyst. be accomplished by any of the suitable methods 2, A selective hydrodesulfurization process whlcl} are conventlonauy employed at h which comprises removing sulfur from petroleum out time. For example, catalyst vapor disengaghydrocarbons by fractionating a petroleum hyi ing tubes co d e Placed at the Plates Separating drocarbon charge stock into a plurality of frac each reaction zone and a pu as could be intions, contacting the highest boiling fraction troduced at low differential pressure into these with a hydrogenation catalyst in the presence tubes to permit the downward flow of catalyst of a hydrogen-containing gas, combining the next lower boiling fraction with the mixture of said highest boiling fraction and hydrogen-containing gas, heating this mixture to an incrementally higher temperature and contacting this heated mixture with a hydrogenation catalyst at an incrementally higher temperature, and combining each remaining lower boiling fraction with the mixture of the previously combined higher boiling fractions, heating said successive combined mixtures to incrementally higher temperatures and contacting said successive combined and heated mixtures with a hydrogenation catalyst.

3. A selective hydrodesulfurization process which comprises removing sulfur from petroleum hydrocarbons by fractionating a petroleum hydrocarbon charge stock into a plurality of fractions, contacting a high boiling fraction with a hydrogenation catalyst, in the presence of a hydrogen-containing gas containing suflicient hydrogen to enable the entire charge stock to be hydrodesulfurized, combining a lower boiling fraction with the mixture of said high boiling fraction and hydrogen-containing gas, heating this mixture to an incrementally higher temperature and contacting this heated mixture with a hydrogenation catalyst.

4. A selective hydrodesulfurization process which comprises removing sulfur from petroleum hydrocarbons by fractionating a petroleum hydrocarbon charge stock into a plurality of fractions, contacting the highest boiling fraction with a hydrogenation catalyst, in the presence of a hydrogen-containing gas containing sufficient hydrogen to enable the entire charge stock to be hydrodesulfurized, combining the next lower boiling fraction with the mixture of said highest boiling fraction and hydrogen-containing gas, heating this mixture to an incrementally higher temperature and contacting this heated mixture with a hydrogenation catalyst, combining each remaining lower boiling fraction with the mixture of the previously combined higher boiling fractions heating said successive combined mixtures to incrementally higher temperatures and contacting said successive combined and heated mixtures with a hydrogenation catalyst.

5. A selective hydrodesulfurization process which comprises absorbing sulfur from petroleum hydrocarbons by fractionating a petroleum hydrocarbon charge stock into a plurality of fractions, contacting a high boiling fraction with a contact agent selected from the group consisting of iron group metals, metal oxides and combinations thereof on a carrier, in the presence of a hydrogen-containing gas, absorbing sulfur from the petroleum hydrocarbons to form an iron group metal sulfide on the contact, combining a lower boiling fraction with the mixture of said high boiling fraction and hydrogen-containing gas and contacting the combined mixture at an incrementally higher temperature, with a contact agent selected from the group consisting of an iron group metal, metal oxides and combinations thereof on a carrier, and absorbing sulfur from the petroleum hydrocarbons to form iron group metal sulfide on the contact.

6. A selective hydrodesulfurization process which comprises absorbing sulfur from petroleum hydrocarbons by fractionating a petroleum hydrocarbon charge stock into a plurality of fractions, contacting the highest boiling fraction with a contact agent selected from the group consisting of iron group metals, metal oxides and combinations thereof on a carrier, in the presence of a hydrogen-containing gas, absorbing sulfur from the petroleum hydrocarbons to form an iron group metal sulfide on the contact, combining the next lower boiling fraction with the mixture of said highest boiling fraction and hydrogen-containing gas and contacting the combined mixture at an incrementally higher temperature, with a contact agent selected from the group consisting of iron group metals, metal oxides and combinations thereof on a carrier, absorbing sulfur from the petroleum hydrocarbons to 'form iron group metal sulfide on the contact, combining each remaining lower boiling fraction with the mixture of the previously combined higher boiling fractions, and contacting said successive combined mixtures with a contact agent selected from the group consisting of iron group metals, metal oxides and combinations thereof on a carrier.

7. A selective hydrodesulfurization process which comprises removing sulfur from petroleum hydrocarbons by fractionating a petroleum hydrocarbon charge stock into a plurality of fractions, contacting a high boiling fraction with a contact agent selected'from the group consisting of nickel, nickel oxide and combinations thereof on a carrier, in the presence of a hydro gen-containing gas, absorbing sulfur from the petroleum hydrocarbons to form nickel sulfides on the contact, combining a lower boiling fraction with the mixture of said high boiling fraction and hydrogen-containing gas and contacting the combined mixture at an incrementally higher temperature with a contact agent selected from the group consisting of nickel, nickel oxide and combinations thereof on a carrier, absorbing sulfur from the petroleum hydrocarbons to form nickel sulfide on the contact.

8. A selective hydrodesulfurization process which comprises removing sulfur from petroleum hydrocarbons by fractionating a petroleum hydrocarbon charge stock into a plurality of fractions, contacting the highest boiling fraction with a contact agent selected from the group consisting of nickel, nickel oxide and combinations thereof on a carrier, in the presence of a hydrogen-containing gas, absorbing sulfur from the petroleum hydrocarbons to form nickel sulfide on the contact, combining the next lower boiling fraction with the mixture of said highest boiling fraction and hydrogen-containing gas and contacting the combined mixture at an incrementally higher temperature with a contact agent-selected from the group consisting of nickel, nickel oxide and combinations thereof on a carrier. absorbing sulfur from the petroleum hydrocarbons to form nickel sulfide on the contact, and combining each remaining lower boiling fraction with the mixture of the previously combined higher boiling fractions, and contacting said successive combined mixtures with a contact agent selected from the group consisting of nickel, nickel oxide and combinations thereof on a carrier.

9. A selective hydrodesulfurization process which comprises removing sulfur from petroleum hydrocarbons by fractionating a petroleum hydrocarbon charge stock into a plurality of fractions, contacting a high boiling fraction with a contact agent selected from the group consisting of iron group metals, metal oxides and combinations thereof on a carrier, in the presence of a hydrogen-containing gas, absorbing sulfur from the petroleum hydrocarbons to form iron group sulfide on the contact, combining a lower boiling fraction with the mixture of said high boiling fraction and hydrogen-containing gas,

and contacting the combined mixture at an incrementally higher temperature with a contact agent selected from the group consisting of iron group metals, metal oxides and combinations thereof on a carrier, absorbing sulfur from the petroleum hydrocarbons to form iron group metal sulfide on the contact, and continuing said process until regeneration of the contact is required, then regenerating said contact material to substantially its original form.

10. A selective hydrodesulfurization process which comprises removing sulfur from petroleum hydrocarbons by fractionating a petroleum hydrocarbon charge stock into a plurality of fractions, contacting the highest boiling fraction with a contact agent selected from the group consisting of nickel, nickel oxide, and combinations thereof on a carrier, in the presence of a hydrogen-containing gas, absorbing sulfur from the petroleum hydrocarbons to form nickel sulfide on the contact, combining the next lower boiling fraction with the mixture of said highest boiling fraction and hydrogen-containing gas, and contacting the combined mixture at an incrementally higher temperature with a contact agent selected from the group consisting of nickel, nickel oxide, and combinations thereof on a carrier, absorbing sulfur from the petroleum hydrocarbons to form nickel sulfide on the contact, combining each remaining lower boiling fraction with the mixture of the previously combined higher boiling fractions and contacting said successive combined mixtures with a contact agent selected from the group consisting of nickel, nickel oxide, and combinations thereof on a carrier. at incrementally higher temperatures, absorbing sulfur from the petroleum hydrocarbons to form nickel sulfide on the contact, and continuing said process until substan ial amounts of hydrogen sulfide appear in the eiiluent, and the nickel content of the contact has been substantially converted into nickel sulfide, then regenerating said contact material to substantially its original form.

11. A selective hydrodesulfurization process which comprises removing sulfur from retroleum hydrocarbons by fractionating a high boiling petroleum hydrocarbon charge stock into a plurality of fractions, said fractions being substantially in the vapor state, contacting the highest boiling fraction with a contact agent selected from the group consisting of iron group metals, metal oxides, and combinations thereof on a carrier, in the presence of a hydrogen-containing gas at a temperature of between 650 and 750 F., absorbing sulfurfrom the hydrocarbon vapors to form iron group metal sulfide on the contact, combining the next lower boiling fraction with a mixture of said highest boiling fraction and hydrogen-containing gas, and contacting the combined mixture at an incrementally higher temperature with a contact agent selected from the group consisting of iron group metals, metal oxides, and combinations thereof on a carrier, absorbing sulfur from the hydrocarbon vapors to form iron group metal sulfides on the contact, and combining each remaining lower boiling fraction with the mixture of the previously combined higher boiling fractions. and. contacting said successive combined mixtures with a contact agent selected from the group consistingof iron group metals, metal oxides and combinations thereof on a carrier at incrementally higher temperatures, absorbing sulfur from the hydrocarbon vapors to form iron group metal sulfide on the contact, so that the lowest boiling fraction is introduced at a temperature of between 850 and 950? F.

12. A selective hydrodesulfurization process which comprises removing sulfur from petroleum hydrocarbonsby fractionating a crude petroleum hydrocarbon charge stock into a plurality of fractions, said fractions being substantially the vapor phase and consisting of gasoline, naphtha, light gas oil, heavy gas oil, and bottoms,- contacting the bottoms with a contact agent 'selected from the group consisting of nickel, nickel oxide and combinations thereof supported on a carrier at a temperature of about 700 F., in the presence of a hydrogen-containing gas containing sufiicient hydrogen to hydrodesulfurize the original petroleum hydrocarbon charge stock, absorbing sulfur from the hydrocarbon vapors to form nickel sulfide on the contact, then, combining with this fraction the heavy gas oil and contacting with a similar contact agent at a temperature of about 750 F., absorbing sulfur from the hydrocarbon vapors to form nickel sulfide on the contact, then combining the light gas oil with the mixture of heavy gas oil, bottoms and hydrogen-containing gas and contacting said mixture with a similar contact agent at a temperature of about 800 F., absorbing sulfur from the hydrocarbon vapors to form nickel sulfide on the contact, then combining the naphtha with the mixture of light gas oil, heavy gas oil, bottoms and hydrogen-containing gas, and contacting the combined mixture with a similar contact agent at a temperature of about 850 F., absorbing sulfur from the hydrocarbon vapors to form nickel sulfide on the contact, then combining the gasoline with the combined mixture of naphtha, light gas oil, heavy gas oil, bottoms and hydrogen-containing gas and contacting the combined mixture with a similar contact agent at a temperature of about 900 F., absorbing sulfur from the hydrocarbon vapors to form nickel sulfide on the contact, and continuing said process until substantial amounts of hydrogen sulfide appear in the effluent, and before the available nickel content of the contact has been entirely converted into nickel sulfide.

LESLIE U. FRANKLIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name 7 Date 2,073,578 Gwynn Mar. 9, 1937 2,174,510 Gwynn Oct. 3, 1939 2,371,298 Hudson Mar. 13, 1945 FOREIGN PATENTS Number Country Date a i a n Wan- July 2 1 8 

1. A SELECTIVE HYDRODESULFURIZATION PROCESS WHICH COMPRISES REMOVING SULFUR FROM PETROLEUM HYDROCARBONS FOR FRACTIONATING A PETROLEUM HYDROCARBON CHARGE STOCK INTO A PLURALITY OF FRACTIONS, CONTACTING A HIGH BOILING FRACTION WITH A HYDROGENATION CATALYST IN THE PRESENCE OF A HYDROGEN-CONTAINING GAS, COMBINING A LOWER BOILING FRACTION WITH THE MIXTURE OF SAID HIGH BOILING FRACTION AND HYDROGEN-CONTAINING GAS, HEATING THIS MIXTURE TO AN INCREMENTALLY HIGHER TEMPERATURE AND CONTACTING THIS HEATED MIXTURE WITH A HYDROGENATION CATALYST. 